Node.js Manual & Documentation

Table Of Contents

net 网络模块

The net module provides you with an asynchronous network wrapper. It contains methods for creating both servers and clients (called streams). You can include this module with require("net");


net.createServer([options], [connectionListener])

Creates a new TCP server. The connectionListener argument is automatically set as a listener for the 'connection' event.


options is an object with the following defaults:

options参数为一个对象,默认值如下: { allowHalfOpen: false }

If allowHalfOpen is true, then the socket won't automatically send FIN packet when the other end of the socket sends a FIN packet. The socket becomes non-readable, but still writable. You should call the end() method explicitly. See 'end' event for more information.



Construct a new socket object and opens a socket to the given location. When the socket is established the 'connect' event will be emitted.


The arguments for this method change the type of connection:



This class is used to create a TCP or UNIX server.


Here is an example of a echo server which listens for connections on port 8124:


var net = require('net');
var server = net.createServer(function (c) {
server.listen(8124, 'localhost');

Test this by using telnet:


telnet localhost 8124

To listen on the socket /tmp/echo.sock the last line would just be changed to

如要监听socket /tmp/echo.sock,最后一行代码需要修改成:


Use nc to connect to a UNIX domain socket server:


nc -U /tmp/echo.sock

net.Server is an EventEmitter with the following events:

net.Server是下列事件的 EventEmitter(事件触发器):

server.listen(port, [host], [callback])

Begin accepting connections on the specified port and host. If the host is omitted, the server will accept connections directed to any IPv4 address (INADDR_ANY).


This function is asynchronous. The last parameter callback will be called when the server has been bound.


One issue some users run into is getting EADDRINUSE errors. Meaning another server is already running on the requested port. One way of handling this would be to wait a second and the try again. This can be done with

一些用户可能会遇到EADDRINUSE 错误,该错误消息的意思是已经有另一个服务运行在请求的端口上,一个解决方法就是等一会再试一下,就像下面的代码这样:

server.on('error', function (e) {
  if (e.code == 'EADDRINUSE') {
    console.log('Address in use, retrying...');
    setTimeout(function () {
      server.listen(PORT, HOST);
    }, 1000);

(Note: All sockets in Node are set SO_REUSEADDR already)


server.listen(path, [callback])

Start a UNIX socket server listening for connections on the given path.

启动一个UNIX socket服务,监听指定的path路径上的连接。

This function is asynchronous. The last parameter callback will be called when the server has been bound.



Start a server listening for connections on the given file descriptor.


This file descriptor must have already had the bind(2) and listen(2) system calls invoked on it.

此文件描述符上必须已经执行了 bind(2)listen(2) 系统调用。


Stops the server from accepting new connections. This function is asynchronous, the server is finally closed when the server emits a 'close' event.



Returns the bound address of the server as seen by the operating system. Useful to find which port was assigned when giving getting an OS-assigned address



var server = net.createServer(function (socket) {

// grab a random port.
server.listen(function() {
  address = server.address();
  console.log("opened server on %j", address);


Set this property to reject connections when the server's connection count gets high.



The number of concurrent connections on the server.


Event: 'connection' 事件:'connection'

function (socket) {}

Emitted when a new connection is made. socket is an instance of net.Socket.


Event: 'close'

function () {}

Emitted when the server closes.



This object is an abstraction of of a TCP or UNIX socket. net.Socket instances implement a duplex Stream interface. They can be created by the user and used as a client (with connect()) or they can be created by Node and passed to the user through the 'connection' event of a server.

这是TCP或UNIX socket的抽象对象。net.Socket实例实现了一个全双工的流接口。此实例可以是由用户建立用作客户端(使用connect()方法),也可能由Node建立并通过服务器的'connection'事件传给用户。

net.Socket instances are EventEmitters with the following events:

net.Socket 的实例是下列事件的事件触发器:

new net.Socket([options])

Construct a new socket object.


options is an object with the following defaults:


{ fd: null
  type: null
  allowHalfOpen: false

fd allows you to specify the existing file descriptor of socket. type specified underlying protocol. It can be 'tcp4', 'tcp6', or 'unix'. About allowHalfOpen, refer to createServer() and 'end' event.


socket.connect(port, [host], [callback])

socket.connect(path, [callback])

Opens the connection for a given socket. If port and host are given, then the socket will be opened as a TCP socket, if host is omitted, localhost will be assumed. If a path is given, the socket will be opened as a unix socket to that path.

打开一下指定socket的连接。如果给出了porthost,将作为一个TCP socket打开,如果省略了host,将默认连接到localhost。如果指定了path,该socket将作为一个UNIX socket打开,并连接到path路径。

Normally this method is not needed, as net.createConnection opens the socket. Use this only if you are implementing a custom Socket or if a Socket is closed and you want to reuse it to connect to another server.

通常情况下该方法并不需要,使用 net.createConnection 就可以打开socket。只有在你实现一个自定义的socket,或者你想重用一个已经关闭的socket连接到另一个服务器。

This function is asynchronous. When the 'connect' event is emitted the socket is established. If there is a problem connecting, the 'connect' event will not be emitted, the 'error' event will be emitted with the exception.

这个函数是异步函数。当发生 'connect'事件时socket被建立,如果连接遇到问题, 'connect'事件不会被触发,而携带异常信息的'error' 事件将被触发。

The callback parameter will be added as an listener for the 'connect' event.

参数callback将作为 connect事件的监听器被增加进来。


net.Socket has the property that socket.write() always works. This is to help users get up an running quickly. The computer cannot necessarily keep up with the amount of data that is written to a socket - the network connection simply might be too slow. Node will internally queue up the data written to a socket and send it out over the wire when it is possible. (Internally it is polling on the socket's file descriptor for being writable).


The consequence of this internal buffering is that memory may grow. This property shows the number of characters currently buffered to be written. (Number of characters is approximately equal to the number of bytes to be written, but the buffer may contain strings, and the strings are lazily encoded, so the exact number of bytes is not known.)


Users who experience large or growing bufferSize should attempt to "throttle" the data flows in their program with pause() and resume().



Sets the encoding (either 'ascii', 'utf8', or 'base64') for data that is received.

设置接收到的数据的编码(可以是'ascii''utf8''base64') 。


This function has been removed in v0.3. It used to upgrade the connection to SSL/TLS. See the TLS for the new API.


socket.write(data, [encoding], [callback])

Sends data on the socket. The second parameter specifies the encoding in the case of a string--it defaults to UTF8 encoding.


Returns true if the entire data was flushed successfully to the kernel buffer. Returns false if all or part of the data was queued in user memory. 'drain' will be emitted when the buffer is again free.

在所有数据被成功的写入系统内核缓冲区时返回true,如果全部或部分数据进入了用户内存的队列则返回false。 当缓冲区再次变空时,'drain' 事件将被触发。

The optional callback parameter will be executed when the data is finally written out - this may not be immediately.

可选参数callback 将在数据最终被写出时执行——可能不是立即执行。

socket.write(data, [encoding], [fileDescriptor], [callback])

For UNIX sockets, it is possible to send a file descriptor through the socket. Simply add the fileDescriptor argument and listen for the 'fd' event on the other end.

对于UNIX socket,可以通过socket发送一个文件描述符,简单的增加参数 fileDescriptor,并在另一端监听'fd'事件。

socket.end([data], [encoding])

Half-closes the socket. I.E., it sends a FIN packet. It is possible the server will still send some data.


If data is specified, it is equivalent to calling socket.write(data, encoding) followed by socket.end().

如果指定了data ,等同于依次调用socket.write(data, encoding)socket.end()


Ensures that no more I/O activity happens on this socket. Only necessary in case of errors (parse error or so).



Pauses the reading of data. That is, 'data' events will not be emitted. Useful to throttle back an upload.



Resumes reading after a call to pause().


socket.setTimeout(timeout, [callback])

Sets the socket to timeout after timeout milliseconds of inactivity on the socket. By default net.Socket do not have a timeout.

设置socket不活动时间超过timeout 毫秒后进入超时状态。默认情况下net.Socket不会超时。

When an idle timeout is triggered the socket will receive a 'timeout' event but the connection will not be severed. The user must manually end() or destroy() the socket.


If timeout is 0, then the existing idle timeout is disabled.

如果 timeout设置成0,已经存在的闲置超时将被禁用。

The optional callback parameter will be added as a one time listener for the 'timeout' event.

可选参数callback 将作为一次性监听器添加到 'timeout' 事件。


Disables the Nagle algorithm. By default TCP connections use the Nagle algorithm, they buffer data before sending it off. Setting noDelay will immediately fire off data each time socket.write() is called.


socket.setKeepAlive(enable=false, [initialDelay])

Enable/disable keep-alive functionality, and optionally set the initial delay before the first keepalive probe is sent on an idle socket. Set initialDelay (in milliseconds) to set the delay between the last data packet received and the first keepalive probe. Setting 0 for initialDelay will leave the value unchanged from the default (or previous) setting.



The string representation of the remote IP address. For example, '' or '2001:4860:a005::68'.


This member is only present in server-side connections.


Event: 'connect' 事件:'connect'

function () { }

Emitted when a socket connection successfully is established. See connect().

当一个socket连接成功建立时触发,参考 connect()

Event: 'data' 事件:'data'

function (data) { }

Emitted when data is received. The argument data will be a Buffer or String. Encoding of data is set by socket.setEncoding(). (See the section on Readable Socket for more information.)

当收到数据时触发,参数data将是一个缓冲区(Buffer)或者字符串(String)。数据的编码方式通过socket.setEncoding()设置。( 更多信息请参考章节Readable Socket

Event: 'end' 事件:'end'

function () { }

Emitted when the other end of the socket sends a FIN packet.


By default (allowHalfOpen == false) the socket will destroy its file descriptor once it has written out its pending write queue. However, by setting allowHalfOpen == true the socket will not automatically end() its side allowing the user to write arbitrary amounts of data, with the caveat that the user is required to end() their side now.

默认情况下(allowHalfOpen == false)一旦待写出队列中的内容全部被写出,socket将自动销毁它的文件描述符。然而如果设置allowHalfOpen == true,则socket不会自动调用end(),而是允许用户继续写入任意数量的数据,这种情况下需要用户主动调用end()关闭半连接。

Event: 'timeout' 事件:'timeout'

function () { }

Emitted if the socket times out from inactivity. This is only to notify that the socket has been idle. The user must manually close the connection.


See also: socket.setTimeout()

参考: socket.setTimeout()

Event: 'drain' 事件:'drain'

function () { }

Emitted when the write buffer becomes empty. Can be used to throttle uploads.


Event: 'error' 事件:'error'

function (exception) { }

Emitted when an error occurs. The 'close' event will be called directly following this event.

当有错误发生时触发, 'close' 事件紧跟其后被调用。

Event: 'close' 事件:'close'

function (had_error) { }

Emitted once the socket is fully closed. The argument had_error is a boolean which says if the socket was closed due to a transmission error.

当连接字完全被关闭时触发,参数had_error是一个布尔型变量, 用来说明连接字是否由于一个传输错误而关闭。



Tests if input is an IP address. Returns 0 for invalid strings, returns 4 for IP version 4 addresses, and returns 6 for IP version 6 addresses.



Returns true if input is a version 4 IP address, otherwise returns false.



Returns true if input is a version 6 IP address, otherwise returns false.